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Refrigerant Piping 
Connection
Fig. 7.3 Fig. 7.4
 Oil traps
 CAUTION
• 
If the indoor unit is installed higher than the 
outdoor unit:  
 
An oil trap should be installed every 10m
(32.8ft) of vertical suction line riser.
(See Fig. 7.3)     
-If oil flows back into the outdoor unit’s 
 compressor, this might cause liquid 
 compression or deterioration of oil return. 
 Oil traps in the rising gas piping can prevent 
 this.    
 CAUTION
The indoor unit is installed higher than the 
outdoor unit  
If the outdoor unit is installed higher than the 
indoor unit:  
-It is recommended that vertical suction risers 
not be upsized. Proper oil return to the 
compressor should be maintained with suction 
gas velocity. If velocities drop below7.62m/s
(1500fpm (feet per minute)), oil return will be
decreased. An oil trap should be installed every 
6m(20ft) of vertical suction line riser. 
(See Fig. 7.4)     
The outdoor unit is installed higher than the 
indoor unit